Concrete admixture anti-segregation agent to adjust concrete workability and fluidity coating agent Anhui Yulong professional segregation agent manufacturer

Abnormalities in the setting time of concrete generally manifest as excessive retarding, rapid setting and false setting. There are many factors that influence the abnormal condensation of cement concrete. Concrete admixtures, cement, admixtures, ambient temperature and wind speed may ultimately lead to the occurrence of abnormal condensation of cement concrete. Judging from the quality of concrete projects at this stage, the type of retarder, improper retarder dosage, incompatibility between admixtures and cement, and ambient temperature are the main reasons for abnormal condensation of cement concrete and even accidents in concrete projects.

Causes of excessive retardation of concrete

(1) The retarder component in the concrete admixture is excessive, especially when the sucrose content is high;

(2) Overmixing of concrete admixtures caused by human or mechanical failure;

(3) Mistaken use of fly ash or mineral powder as cement;

(4) Concrete mix Improper ratio design and too much admixture, especially when the temperature of the concrete pouring environment is low;

(5) Influenced by air temperature, the temperature is too low;

(6) Insufficient maintenance , especially when the temperature is too low;

(7) The air content of concrete is too large, causing the air content of concrete to reach 8-10%;

(8) The slump of concrete is too large or even Separation of bleeding water results in high fly ash content and large water-cement ratio in the surface layer of concrete;

Causes of rapid setting of concrete

(1) No retarder is added to the concrete admixture Or the amount of retarder is not enough;

(2) When cement using anhydrite and fluorine-containing gypsum as the setting regulator, when using lignin sulfonate water-reducing agent, rapid setting of concrete is likely to occur;

(3) The water-to-cement ratio is low, the maintenance is not in place and the ambient temperature is too high. The concrete loses water prematurely due to high winds and accelerates cement hardening;

(4) Sulfaluminum is used Salt cement or high alumina cement;

(5) C3A content in cement is high and alkali content is high;

Causes of false setting in concrete

(1 ) The ambient temperature is too high, the wind is strong, the concrete loses water prematurely, and the maintenance is not in place and it is not covered in time. Especially when high-grade concrete is prepared with carboxylic acid admixtures, the surface of the concrete quickly loses water and becomes hard, while the concrete in the lower layer is still relatively soft. No condensation;

(2) The adsorption of concrete admixtures by cement, admixtures, gravel aggregates, etc. suddenly increases with time, pump pressure, and ambient temperature conditions, and the slump is quickly lost. If it falls off, the concrete will be scattered like tofu. The main reason is that the admixtures and their types are related to changes in the adsorption capacity of cement;

(3) The temperature of the cement is too high, and the dihydrate gypsum in the cement dehydrates and turns into hemihydrate gypsum or anhydrous gypsum;

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Solution:

(1) In summer, it is best not to use cement with a temperature exceeding 80°C to mix concrete in a concrete mixing station;

(2) In summer, use underground Cold water (add ice if necessary);

(3) Maintain concrete in time to prevent premature loss of water or freezing;

(4) Before construction, make cement and Adaptability test of concrete admixtures, mixing concrete to observe fluidity loss, and examining the setting time of concrete at the prevailing temperature. Determine the suitability of concrete admixtures;

(5) Maintenance of mixing station instruments and equipment for reliable operation;

(6) Concrete admixture products must be inspected, reliable, and of stable quality;

(7) Appropriate concrete mix ratio;

(8) When encountering abnormally solidified concrete, analyze the specific problems in detail and remove them as soon as possible if they endanger the quality of the project. The sooner the better. Generally speaking, if excessive retardation exceeds 4 days, the loss of concrete strength will be serious; when false concrete setting occurs, cement mortar of the same strength grade can be used to remix the concrete before pouring or use the mortar to plaster the concrete surface. Collect light. After the concrete is quickly set, if it is not poured into the formwork, it will be discarded. If it is poured into the formwork, it will be cut out or retained depending on the specific situation.